Gumpaste

So I haven't worked with gum paste very much but I am trying to make a Minnie Mouse cake and I need to make her ears and bow. I plan to make them a couple of days before I place them on the cake but about how long will they actually take to dry and if I let them sit out to long with they end up having that elephant skin pattern on them. One last thing abou how thick would you make the ears? Thanks so much in advance